System for engaging an electromagnetic clutch during range change operation

Abstract

A system for controlling the clutch current of an electromagnetic clutch for a vehicle which has an automatic transmission and a select lever for selecting driving ranges in the transmission. A driving range switch is provided to be operated when the select lever is operated to select a driving range. A logic gate circuit is provided to respond to a signal of the select lever switch for allowing the clutch current to flow. A delay circuit responds to the signal of the driving range switch for producing an output with a delay and for opening the logic gate circuit, whereby the clutch is engaged for a predetermined period after the operation of the select lever.

What is claimed is: 
     
       1. A system for controlling clutch current of an electromagnetic clutch which current produces engagement of the electromagnetic clutch in a vehicle having an engine, an automatic transmission with the clutch being connected between the engine and the automatic transmission, and a select layer selectively moveable to respective positions corresponding to first and second driving ranges of the automatic transmission which ranges are different in transmission performance and in which ranges the clutch current engages the clutch, comprising: a first driving range switch and a second driving range switch respectively operated at the respective positions of the select lever producing first and second signals respectively;   delay means responsive, during operation of the select lever, to termination of the first and second signals immediately producing respecitively a third signal terminating with delay and a fourth signal terminating with delay after the resepctive termination of the first and second signals;   gate means, responsive to the third and fourth signals respectively, providing the clutch current, whereby the clutch is continuously engaged during the operation of the select lever away from said positions, during said delay   
     
     
       2. The system according to claim 1 wherein the gate means comprises logic gates and a transistor responsive to a signal from one of the logic gates for allowing the clutch current to flow. 
     
     
       3. The system according to claim 2 wherein the first driving range switch and the second driving range switch operates to produce respectively said first signal and said second signal when each respective switch is turned off.   
     
     
       4. The system as set forth in claim 1, wherein said delay means comprises two inverters connected in series and a capacitor connected in parallel across one of said inverters.   
     
     
       5. The system as set forth in claim 1, wherein said gate means comprises a NAND gate having one input connected to an output of delay means and another input connected to a corresponding of said driving range switches receiving a corresponding of said first and second signals.   
     
     
       6. The system as set forth in claim 5, wherein said gate means comprises two of said NAND gates and said delay means comprises two delay circuits respectively operatively connected to a corresponding of said driving range switches.   
     
     
       7. The system as set forth in claim 6, wherein said gate means further comprises an OR gate connected to the outputs of said NAND gates.   
     
     
       8. The system as set forth in claim 1, wherein said delay means further produces said third and fourth signals respectively in response to said first and second signals.   
     
     
       9. A system for controling clutch current of an electromagnetic clutch which current produces engagement of the electromagnetic clutch in a vehicle having an engine, an automatic transmission with the clutch being connected between the engine and the automatic transmission, and a select lever selectively moveable to respective positions corresponding to first and second driving ranges of the automatic transmission which ranges are different in transmission performance, comprising: a first driving range switch and a second driving range switch respectively operated only at the respective positions of the select lever corresponding to the first and second driving ranges producing first and second signals respectively;   gate means responsive to said first and second signals respectively providing the clutch current to engage the clutch;   delay means responsive, during operation of the select lever away from the respective positions of the select lever, to termination of the first and second signals respectively producing respectively, a third signal continuing for a delay time and a fourth signal continuing for a delay time after the respective termination of the first and second signals;   said gate means is further responsive to the third and fourth signals respectively providing clutch current whereby the clutch is continuously engaged during the operation of the select lever away from said positions, during said delay time.   
     
     
       10. The system as set forth in claim 9, wherein said first and second driving ranges are a normal driving range and a high engine speed driving range, respectively.   
     
     
       11. The system as set forth in claim 9, wherein said transmission is an infinitely variable transmission.   
     
     
       12. The system as set forth in claim 9, wherein said electromagnetic clutch is a magnetic powder clutch.   
     
     
       13. The system as set forth in claim 9, wherein said gate means is further responsive to absence of all said signals for disengaging the clutch in a neutral position of the select lever.